Phylogenetic relationships and taxonomic revision of the genus Macrocoeloma Miers, 1879 (Crustacea: Decapoda: Brachyura)

Author(s)

Jéssica Colavite

• Document type: Doctoral Thesis
• Press: Botucatu. 2020-04-23.
• Institution: Universidade Estadual Paulista (Unesp). Instituto de Biociências. Botucatu
• Defense date: 2020-02-21
• Advisor: William Ricardo Amancio Santana; Amanda Marie Windsor

Abstract

The amphi-American genus, Macrocoeloma Miers, 1879, is composed of decorator crabs from tropical and subtropical regions. These crabs are found on distinct substrates, including mainly coral reefs and rock. Macrocoeloma has undergone several systematic changes in its family status, since the original description until its recent exclusion of Mithracidae. Prior to this study, Macrocoeloma was considered incertae sedis, due to little knowledge of the relationships between species of the genus and related genera, and its taxonomic revision has been suggested several times in the literature. Thus, in order to address these taxonomic and phylogenetics gaps, this study employed morphological and molecular approaches to reconstruct the phylogenetic relationships of Macrocoeloma. We used a combined molecular dataset of a nuclear (18S) and three mitochondrial genes (12S, 16S, COI) using Maximum Likelihood and Bayesian Inference. In addition, the inference of species delimitation was performed with the Poisson tree processes model (PTP), using Maximum Likelihood phylogeny of the mitochondrial COI gene. The taxonomic revision of Macrocoeloma was provided with elaborated diagnosis, detailed descriptions and maps of geographic distribution based on examined material. The monophyly of Macrocoeloma was demonstrated after exclusion of Pericera heptacantha and P. septemspinosa. The monotypic genus Thersandrus Rathbun, 1897 is a sister group of Macrocoeloma, followed by the new genus proposed to accommodate P. heptacantha and P. septemspinosa. Macrocoeloma, Thersandrus and the new genus belong to the family Pisidae. The species complex formed by M. trispinosum (Latreille, 1825) and M. nodipes (Desbonne in Desbonne & Schramm, 1867), despite of the low statistical support, are treated here as two valid species, considering their morphological distinction. The Macrocoeloma outlandish record for the Fiji Islands, M. trigonum Dana, 1852, is probably a label error, with the location being corrected for Rio de Janeiro city. The Brazilian morphotype previously identified as M. trispinosum (Latreille, 1825) was re-determined as M. trigonum, being a valid species with morphological and molecular support. After this study, Macrocoeloma concavum, M. euthecum and, M. laevigatum also had their range of occurrences expanded to the southeastern coast of Brazil. (AU)

• FAPESP's process: 16/02775-8 - Phylogenetic relationship and a taxonomic review of the genus Macrocoeloma Miers, 1879 (Crustacea: Decapoda: Brachyura)
• Grantee: Jéssica Colavite
• Support Opportunities: Scholarships in Brazil - Doctorate